Resin composition

ABSTRACT

There is disclosed a resin composition comprising: 
     (a) 28 to 78% by weight of a polyamide resin, 
     (b) 20 to 70% by weight of a polyphenylene ether resin, 
     (c) 2 to 40% by weight of a block copolymer composed of an alkenyl aromatic polymer and a conjugated diene polymer wherein a content of an alkenyl aromatic polymer structure unit is 10 to 45% by weight and at least 50% of a conjugated diene polymer structure unit is hydrogenated and 
     (d) at least one compound selected from the group consisting of α,β-unsaturated dicarboxylic acid, an acid anhydride and derivatives thereof with an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the sum of Components (a), (b) and (c), 
     which has a specific dispersion state. 
     The resin composition has excellent thermal stability and also good balance between impact strength, rigidity and high temperature rigidity with high degree.

BACKGROUND OF THE INVENTION

This invention relates to a resin composition comprising a polyamideresin, a polyphenylene ether resin, a block copolymer and α,β-unsaturated dicarboxylic acid or a derivative thereof, moreparticularly to a resin composition having excellent impact strength,and excellent balance in heat-resisting rigidity, heat-resisting agingproperty and molding property, and also available as a material forinjection molding, extrusion molding and blow molding such as a memberin the fields of automobile, electric and electronic.

Polyamide resin has widely been used as one of the representativeengineering plastics excellent in heat resistance, oil resistance andmolding property. However, this resin has defects that characteristicsof dimensional stability, hygroscopicity, heat-resisting deformationproperty under high load and impact resistance are poor.

On the other hand, polyphenylene ether resin has been admitted asengineering plastics having excellent heat resistance, dimensionalstability, non-hygroscopicity and electric characteristics, but thereare defects that melt flowability is bad, working by molding isdifficult and oil resistance and impact resistance are poor.

Thus, in order to provide a molding material without impairing merits ofboth materials and complementing each defects, various compositions havebeen proposed. For example, compositions wherein both of the resins aresimply melted and mixed are disclosed in U.S. Pat. Nos. 3,379,792 and4,338,421 and Japanese Patent Publications No. 997/1970 and No.41663/1984. However, the polyamide resin and the polyphenylene etherresin are inherently bad in compatibility and thus, in such simpleblended systems, affinity at the interface is poor and phase separationis caused at molding so that a composition excellent in mechanicalstrength cannot be obtained.

Accordingly, some methods for improving compatibility of the polyamideresin and the polyphenylene ether resin have been proposed. For example,a method in which a compound having a carbon-carbon double bond and afunctional group such as a carboxyl group, acid anhydride group,acidamide group and imide group is added as a third component (JapaneseProvisional Patent Publication No. 26913/1981), and a method in which acopolymer of styrene type compound and an α, β-unsaturated dicarboxylicacid is blended (Japanese Patent Publication No. 33614/1984). However,impact resistance is still insufficient even in these compositions, sothat further improvement has been desired.

In order to improve impact resistance of a multiple-component polymerblended material such as a polyamide resin and a polyphenylene etherresin, it has been considered to mix and disperse an elastomer which isan improver for impact strength. Further, such a multiple-componentmaterial containing mutually incompatible components causes phaseseparation so that various characteristics have been considered to begreatly depending upon phase separation structure.

For example, there has been proposed in Japanese Provisional PatentPublication No. 27254/1987, a multi-phase structural material that, in athree-component system material comprising a polyamide resin, apolyphenylene ether resin and a specific A--B--A' type diene seriesblock copolymer, when melting viscosities of the polyamide resin and thepolyphenylene ether resin satisfy specific relationship, the polyamideresin exists as a continuous phase, the polyphenylene ether resin as aprimary dispersed phase and the block copolymer as further secondarydispersed phase in the primary dispersed phase. According to thedetailed description of the invention of the patent, there are describedthat composition ratio and viscosity ratio of the polyamide resincomponent and the polyphenylene ether resin component are importantfactors and selecting these suitably, the primary dispersed phase of thepolyphenylene ether resin component is controlled in a suitable particlesize range whereby properties such as impact strength and rigidity canbe improved. However, it cannot be said that heat-resisting agingproperty, impact resistance and rigidity are sufficient.

Also, in Japanese Provisional Patent Publication No. 79258/1989, thereis proposed a polyphenylene ether polyamide composition in which ahydrogenated block copolymer having a content of a vinyl aromaticcompound and molecular weight in specific ranges is used as a thirdcomponent. There are described that when this composition forms aspecific multi-phase structure, i.e. the polyamide forms a continuousphase, the polyphenylene ether component exists as a dispersed phasehaving a specific grain diameter size and the block copolymer is beingpresent with the secondary dispersed state in the polyphenylene etherdispersed phase, the product shows properties excellent in balance suchas heat-resisting deformation, impact resistance, oil resistance andrigidity. However, impact resistance cannot yet be said to besufficient.

SUMMARY OF THE INVENTION

An object of the present invention is, under such a circumstance, toprovide a resin composition which has characteristics of a polyamideresin and a polyphenylene resin simultaneously, i.e. excellent in heatresistance and also highly excellent balance in impact resistance,rigidity and high temperature rigidity.

In order to accomplish the above objects, the present inventors haveintensively studied how to disperse a block copolymer which is an impactstrength improver. As the results, they have found that only when a meltviscosity ratio of the block copolymer and the polyphenylene ether resinis present in a specific range, impact resistance is remarkably improvedat which a multi-phase structure is formed, whereby accomplished thepresent invention.

That is, the resin composition of the present invention comprises

(a) 28 to 78% by weight of a polyamide resin,

(b) 20 to 70% by weight of a polyphenylene ether resin,

(c) 2 to 40% by weight of a block copolymer composed of an alkenylaromatic polymer and a conjugated diene polymer wherein a content of analkenyl aromatic polymer structure unit is 10 to 45% by weight and atleast 50% of a conjugated diene polymer structure unit is hydrogenatedand

(d) at least one compound selected from the group consisting of α,β-unsaturated dicarboxylic acid, an acid anhydride and derivativesthereof with an amount of 0.01 to 10 parts by weight based on 100 partsby weight of the sum of Components (a), (b) and (c),

Component (b) being present in Component (a) as a primary dispersedphase, Component (c) forming a secondary dispersed phase in Component(b), an average particle size of Component (c) being in the range of0.01 to 3 μm, and a melt viscosity ratio (η_(c) /η_(b)) of Component (c)and Component (b) being in the range of 0.09 to 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the present invention will be described in moredetail.

The polyamide resin of Component (a) to be used in the present inventionhas a -CONH- bond in the polymer main chain and can be melted underheating. Representative examples may include polyamide-4, polyamide-6,polyamide-6,6, polyamide-4,6, polyamide-12 and polyamide-6,10, and a lowcrystallinity or amorphous polyamide containing monomer components suchas other known aromatic diamine and aromatic dicarboxylic acid, andtransparent Nylon (trade name), and mixtures thereof may be used.

The polyamide resin (a) to be preferably used in the present inventionis polyamide-6,6 (polyhexamethylene adipamide), polyamide-6(polycapramide) and amorphous polyamide.

The polyamide resin to be used in the present invention preferably has arelative viscosity (measured at 25° C., in 98% conc. sulfuric acid,according to JIS K6810 test method) of 2.0 to 8.0.

The polyphenylene ether resin of Component (b) to be used in the presentinvention has a structural unit represented by the following formula:##STR1## wherein the ether oxygen atom of one unit is connected to thebenzene nucleus of the adjacent unit, n is at least 50, R¹, R², R³ andR⁴ each independently represent a monovalent group selected from thegroup consisting of hydrogen atom, halogen atoms, hydrocarbon groupscontaining no tertiary α-carbon atom, halohydrocarbon groups having atleast 2 carbon atoms between halogen atom and benzene nucleus,hydrocarbonoxy groups, and halohydrocarbonoxy groups having at least 2carbon atoms between halogen atom and benzene nucleus.

In the above formula (I), examples of the hydrocarbon groups containingno tertiary α-carbon atom represented by R¹, R², R³ and R⁴ may includelower alkyl groups such as methyl group, ethyl group, propyl group,isopropyl group and butyl group; alkenyl groups such as vinyl group,allyl group, butenyl group and cyclobutenyl group; aryl groups such asphenyl group, tolyl group, xylenyl group and 2,4,6-trimethylphenylgroup; and aralkyl groups such as benzyl group, phenylethyl group andphenylpropyl group. Examples of halohydrocarbon groups wherein thehalogen atom is substituted through at least two carbon atoms mayinclude 2-chloroethyl group, 2-bromoethyl group, 2-fluoroethyl group,2,2-dichloroethyl group, 2- and 3-bromopropyl groups,2,2-difluoro-3-iodopropyl group, 2-,3-,4- and 5-fluoroamyl groups,2-chlorovinyl group, chloroethylphenyl group, ethylchlorophenyl group,fluoroxylyl group, chloronaphthyl group and bromobenzyl group. As thehydrocarbonoxy groups, there may be included, for example, methoxygroup, ethoxy group, propoxy group, butoxy group, phenoxy group,ethylphenoxy group, naphthoxy group, methylnaphthoxy group, benzoxygroup, phenylethoxy group and triethoxy group. Examples ofhalohydrocarbonoxy groups having at least two carbon atoms betweenhalogen atom and benzene nucleus may include 2-chloroethoxy group,2-bromoethoxy group, 2-fluoroethoxy group, 2,2-dibromoethoxy group, 2-and 3-bromopropoxy groups, chloroethylphenoxy group, ethylchlorophenoxygroup, iodoxyloxy group, chloronaphthoxy group, bromobenzoxy group andchlorotolylethoxy group.

The polyphenylene ether resin to be used in the present invention mayinclude copolymers such as a copolymer of 2,6-dimethylphenol with2,3,6-trimethylphenol, a copolymer of 2,6-dimethylphenol with2,3,5,6-tetramethylphenol and a copolymer of 2,6-diethylphenol with2,3,6-trimethylphenol. Further, the polyphenylene ether to be used inthe present invention also includes modified polyphenylene ethers suchas the polyphenylene ether defined by the above formula (I) having astyrenic monomer (e.g. styrene, p-methylstyrene and α-methylstyrene)grafted thereon.

The methods for preparing the polyphenylene ethers corresponding to theabove have been known in the art, and disclosed in, for example, U.S.Pat. Nos. 3,306,874, 3,306,875, 3,257,357 and No. 3,257,358, andJapanese Patent Publication No. 17880/1977 and Japanese ProvisionalPatent Publication No. 51197/1975.

A group of polyphenylene ether resin (b) preferred for the object of thepresent invention is those having alkyl substituents at the twoortho-positions relative to the ether oxygen atom and a copolymer of2,6-dialkylphenol with 2,3,6-trialkylphenol.

The polyphenylene ether resin (b) to be used in the present inventionpreferably has an inherent viscosity measured at 30° C. in chloroform inthe range of 0.25 to 0.70 dl/g, more preferably 0.30 to 0.60 dl/g andmechanical strength and flowability itself are good.

The block copolymer (c) to be used comprises a polymer having both of analkenyl aromatic polymer block unit and a conjugated diene polymer blockunit in the same molecule and the content of the alkenyl aromaticpolymer unit of 10 to 45% by weight, and at least 50% of double bonds inthe conjugated diene polymer block unit are hydrogenated.

The type of the block bonding may be any type such as the diblock type,triblock type, multiblock type, tapered block type and radial tereblocktype and not particularly limited, but among these, the diblock type andtriblock type are particularly preferred.

Specific examples of a monomer constituting the alkenyl aromatic polymerblock unit may include styrene, paramethyl styrene, α-methylstyrene,vinylxylene, vinylnaphthalene, divinylbenzene, bromostyrene andchlorostyrene, and it may be a combination thereof. Of these, styrene,α-methylstyrene, paramethyl styrene and vinylxylene are preferred, andstyrene is more preferred.

If the ratio of the alkenyl aromatic polymer block unit occupied in theblock copolymer exceeds 45% by weight, impact resistance is lowered, andif it is less than 10% by weight, rigidity will be lowered so that therange other than the above is not preferred.

As specific examples of a monomer constituting the conjugated dienepolymer block unit, there may be included 1,3-butadiene,2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene,and of these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferred.

As a process for producing the alkenyl aromatic polymer-conjugated dieneblock copolymer, a large number of methods have been proposed. Arepresentative method is the method as disclosed in Japanese PatentPublication No. 23798/1965, U.S. Pat. Nos. 3,595,942 and 4,090,996, inwhich block copolymerization is carried out in an inert solvent by useof a lithium catalyst or a Ziegler type catalyst.

Hydrogenation treatment of these block copolymers are conducted byhydrogenating the copolymers in the presence of a hydrogenation catalystin an inert solvent according to the processes as described in, forexample, Japanese Patent Publication No. 8704/1967, No. 6636/1968 or No.20814/1971. In this hydrogenation, at least 50%, preferably 80% or moreof olefinic double bonds in the conjugated diene polymer block arehydrogenated and 25% or less of the aromatic unsaturated bonds in thealkenyl aromatic polymer block may be hydrogenated. As one of such blockcopolymers, there is one commercially sold under trade name of "KRATONG" from Shell Chemical Co.

The viscosity ratio (η_(c) /η_(b)) of a melt viscosity (η_(c)) of theblock copolymer (c) and a melt viscosity (η_(b)) of the polyphenyleneether resin (b) is preferably in the range of 0.09 to 5, more preferablyin the range of 0.3 to 3.0 measuring at a temperature of 280° C. and ashear rate of 100 sec⁻¹. If the viscosity ratio is less than 0.09, theblock copolymer do no disperse in the polyphenylene ether resindispersion phase, and if it exceeds 5, dispersion particles size of theblock copolymer dispersed in the polyphenylene ether resin becomeslarge. Also, a dispersion particle size of the block copolymer which isfurther dispersed in the polyphenylene ether resin dispersion layer isrequired to be in the range of 0.01 to 3 μm, preferably in the range of0.1 to 3 μm, and particularly preferably in the range of 0.1 to 0.7 μm.If it is less than 0.01 μm or exceeding 3 μm, a level of impact strengthbecomes insufficient.

The component (d) to be used in the present invention is at least oneselected from the group consisting of an α, β-unsaturated dicarboxylicacid and acid anhydride, and derivatives thereof. Specifically, theremay be included maleic anhydride, maleic acid, fumaric acid, itaconicacid, maleimide, maleic hydrazide, a reaction product of maleicanhydride and a diamine, for example, those having the structuresrepresented by the following formulae: ##STR2## wherein R represents analiphatic group or an aromatic group, dichloromaleic anhydride andmaleic amide. Of these, maleic anhydride and a mixture of maleicanhydride and maleic acid are suitable.

COMPOSITIONAL RATIO OF THE CONSTITUENT COMPONENTS

In the resin composition of the present invention, a ratio of thepolyamide resin (a) to be occupied therein is in the range of 28 to 78%by weight based on the total weight of the polyamide resin (a), thepolyphenylene ether resin (b) and the block copolymer (c). In order toobtain higher mechanical properties balance, it is more preferred in therange of 35 to 75% by weight, particularly preferably 40 to 70% byweight. If it is less than 28% by weight, a level of oil resistance islow and if it exceeds 78% by weight, heat-resisting rigidity becomesinsufficient.

A ratio of the polyphenylene ether resin (b) to be occupied in the resincomposition of the present invention is in the range of 20 to 70% byweight based on the total weight of the polyamide resin (a), thepolyphenylene ether resin (b) and the block copolymer (c). In order toobtain higher mechanical properties balance, it is more preferred in therange of 20 to 60% by weight, and particularly preferably 25 to 50% byweight. If it is less than 20% by weight, heat-resisting rigidity isinsufficient and if it exceeds 70% by weight, oil resistance and impactstrength become inferior.

When the polyphenylene ether resin with an intrinsic viscosity in therange of 0.3 to 0.6 dl/g generally employed in industry is used due toits good balance in mechanical strength and flowability, if a ratiothereof exceeds 50% by weight based on the total weight of the polyamideresin (a), the polyphenylene ether resin and the block copolymer (c), itbecomes difficult to form a multi-phase structure wherein thepolyphenylene ether resin component becomes a primary dispersion phasewhich is one of the characteristic features of the present invention.

A ratio of the block copolymer (c) to be occupied in the resincomposition of the present invention is in the range of 2 to 40% byweight based on the total weight of the polyamide resin (a), thepolyphenylene ether resin (b) and the block copolymer (c). In order toobtain higher mechanical properties balance, it is more preferred in therange of 5 to 35% by weight, and particularly preferably 7 to 30% byweight. If it is less than 2% by weight, impact strength is insufficientand if it exceeds 40% by weight, heat resistance and rigidity becomelow.

A ratio of the compound of α, β-unsaturated dicarboxylic acid and acidanhydride and derivatives thereof (d) to be occupied in the resincomposition of the present invention is 0.01 to 10 parts by weight,preferably in the range of 0.05 to 5 parts by weight, more preferably0.2 to 2 parts by weight based on the total 100 parts by weight of thepolyamide resin (a), the polyphenylene ether resin (b) and the blockcopolymer (c). If it is less than 0.01 part by weight, impact resistanceis insufficient and if it exceeds 10 parts by weight, difficulty wouldbe caused at appearance of the molded product of the resin composition.

METHOD OF MIXING THE COMPOSITION

Preparation of the resin composition of the present invention can becarried out by use of any method such as the method in which the mixtureis melted and kneaded by use of various kneading machines such as asingle screw extruder, a twin screw extruder and Banbury mixer, themethod in which after mixing solutions or suspensions of each component,removing the solvents, or the method in which a common non-solvent isadded to effect precipitation and then filtered to recover acomposition. Also, order of kneading may be carried out by kneadingwhole components simultaneously or by using previously and preliminarykneaded blend materials. Further, utilizing the difference between themelt viscosities, kneading may be carried out by feeding each componentin the course of an extruder stepwisely. From an economical view point,it is desired to mix all the components simultaneously. In order toimprove impact strength more and more, the method in which kneading iscarried out by a twin screw extruder according to the successive feedingmethod as mentioned below is effective. That is, by using a twin screwextruder having two inlets for fill, Component (b) of the polyphenyleneether resin, Component (c) of the block copolymer, Component (d) of theα, β-unsaturated dicarboxylic acid derivative and a part of Component(a) of the polyamide resin, i.e. not exceeding 50% by weight of theformulated amount of the polyamide resin, preferably 50% by weight orless are fed from the first inlet to effect the first step kneading.Then, the remaining polyamide resin is fed from the second inlet andkneaded to obtain the resin composition of the present invention. Anamount of Component (a) to be added in the first step is preferably 30%by weight or less, more preferably 20% by weight or less, particularlypreferably 5 to 20% by weight based on the total amount of Component (a)to be added. Other third additive components such as a rubber-likepolymer, an inorganic filler, a pigment and a stabilizer may be fed fromeither one of inlets or both inlets by dividing it. The reason why sucha successive feeding method is effective for improving characteristicsof the resin composition is not clear but it can be considered thatmiscibility of the polyphenylene ether resin and the polyamide resin,and the polyphenylene ether resin and the block copolymer are furtherimproved.

Depending on necessity for practical use, other rubber-like polymer, aglass fiber, potassium titanate whisker, an inorganic filler such astalc and calcium carbonate, a pigment, and a stabilizer may beoptionally added.

The resin composition of the present invention maintains characteristicsof both resins of the polyamide and the polyphenylene ether and alsosupplemented defects of the respective resin. Thus, it is excellent inimpact strength, heat-resisting rigidity and heat-resisting agingproperty, and also provides a resin excellent in moldability whereby itis widely available for an industrial material.

EXAMPLES

The present invention is described by referring to Examples, but thepresent invention is not limited in its scope by the Examples at all.

EXAMPLES 1 to 6

Resin compositions were prepared by kneading each composition shown inTable 1 to prepare samples of Examples 1 to 6, respectively. Physicalproperties of these compositions were evaluated and shown in Table 1.

Kneading of the resin is carried out the respective components werethoroughly stirred and mixed by a super mixer, and then melted andkneaded by means of a PCM twin screw mixer manufactured by Ikegai TekkoK.K. at 280° C. and 350 rpm to form into a composition, which was thenextruded into a strand and formed into pellets by a cutter. Since thepolyamide resin has hygroscopicity, for effecting kneading and molding,drying by use of a reduced pressure dryer at the conditions of 0.1 mmHgand 80° C. for 48 hours was carried out immediately before use.

In Examples 1 to 6, resin compositions in which a block copolymerdispersed in the polyphenylene ether resin dispersion layer is ideallydispersed and which are excellent in rigidity, heat resistance andimpact strength can be obtained only when the melt viscosity ratio is inthe range of the present invention.

COMPARATIVE EXAMPLES 1 to 5

In the same manner as in Examples 1 to 6, compositions of Comparativeexamples 1 to 5 were prepared with the compositional ratio shown inTable 1. Physical properties of these compositions were also evaluatedand shown in Table 1.

As the results, in Comparative examples 1 to 3, the melt viscosity ratioof which are out of the range of the present invention, levels ofrigidity and impact resistance are remarkably low so that the effect ofthe present invention is remarkable.

In Comparative example 4, wherein a styrene content of the blockcopolymer is out of the range of the present invention, level of impactresistance is low.

In Comparative example 5, the same procedures are carried out as inExamples 1 to 6 except for using a styrene-butadiene-styrene copolymer(SBS) in place of the block copolymer used therein, and characteristicsthereof were evaluated. In this comparative example 5, it became thecomposition that heat-resisting aging property is markedly lowered andthermal stability in inferior.

Each component used is as follows.

(1) Component (a): Polyamide resin

Polyamide-6 (Novamid-1040, trade name) produced by Mitsubishi KaseiCorporation was used.

(2) Component (b) Polyphenylene ether resin

Three kinds of resins of poly-2,6-dimethyl-1,4-phenylene ether producedexperimentally by Mitsubishi Petrochemical Co., Ltd. having an inherentviscosity measured in chloroform and at 30° C. of 0.51 dl/g, 0.40 dl/gand 0.32 dl/g, respectively, were used.

(3) Component (c): Block copolymer

Hydrogenated styrene-butadiene copolymer (SEBS) (KRATON G-1650, tradename: styrene content of 28% by weight; KRATON G-1651, trade name:styrene content of 33% by weight; KRATON G-1652, trade name: styrenecontent of 29% by weight; and KRATON G-1726, trade name: styrene contentof 30% by weight), and hydrogenated styrene-isoprene copolymer (KRATONGX-1701, trade name: styrene content 37% by weight) all produced byShell Chemical Co., and as the comparative purpose,styrene-butadiene-styrene copolymer (SBS) (KALIFLEX KX-65, trade name)produced by Shell Chemical Co. were used.

Hydrogenated styrene-butadiene-styrene copolymers (Hydrogenated SBS1:styrene content of 40% by weight and Hydrogenated SBS2: styrene contentof 60% by weight) with high styrene contents were used by hydrogenatinga styrene-butadiene-styrene copolymer produced by Nippon SyntheticRubber Co. in Mitsubishi Petrochemical Co., Ltd.

(4) Component (d): Maleic anhydride

Maleic anhydride (reagent grade) commercially available was used.

Evaluating methods of the respective physical property value of thesamples are as shown below.

(1) Preparation of test piece for evaluation

Using an injection molding machine M40A-SJ (trade name) produced byMeiki Seisakusho K.K., a test piece was prepared by subjecting toinjection molding at a cylinder temperature of 280° C. and a moldcooling temperature of 60° C. The test piece was placed in a desiccatorimmediately after preparation thereof, and evaluation was carried outafter allowed to stand at 23° C. for 4 to 6 days.

(2) Measurement and evaluation method

1) MFR:

Melt flow rate was measured at 280° C. under a load of 5 kg according toJIS K7210.

2) Flexural modulus:

Measured according to ISO R178-1974 Procedure 12 (JIS K7203), by use ofInstron tester. Incidentally, the value of flexural modulus at 80° C.was obtained by carrying out the measurement after placing athermostatic chamber so as to place the test piece, and a supportingbase and a pressure wedge portion to be used for measuring in a warm airthermostatic chamber and controlling the state in an atmosphere at 80°C.±1° C. for 20 minutes.

3) Izod impact strength:

Measured according to ISO R¹⁸⁰ -1969 (JIS K710) notched Izod impactstrength, by use of Izod impact tester manufactured by Toyo SeikiSeisakusho.

(3) Heat-resisting aging property:

After treating the test piece in a geer oven manufactured by Toyo SeikiSeisakusho K.K. at 120° C. for 50 hours, Izod impact strength wasmeasured and retaining ratio to the impact strength before heattreatment was calculated.

(4) Melt viscosity:

Shear rate dependency of the melt viscosity at a temperature of 280° C.was measured by an Instron capillary rheometer and calculated theviscosity at a shear rate of 100 sec⁻¹.

(5) Measurement of particle diameter:

A part of the test piece evaluated various physical properties was cutout and after dyeing with OsO₄ and RuO₄, an ultrathin piece was preparedand dispersed form was observed by using a transmission type electronmicroscope with a magnification of 20,000-fold. By the above dyeingmethod, the block copolymer of Component (c) in the resin compositionwas selectively dyed, and as the result, existing state can be confirmedas a black image in the photograph. Using an image analyzing device(SPICCA II manufactured by Nippon Abionics), a diameter d₁ correspondingto a circule equal in area was measured with respect to each dispersionparticle of Component (c). In a sample having a big particle with anaverage particle diameter exceeding 1 micron, the same calculation wascarried out by making observation magnification 5,000-fold. An averageparticle diameter was obtained by the following formula from the aboved₁.

    D=Σnidi.sup.4 /Σnidi.sup.3

wherein ni is a number of particles having a diameter of dicorresponding to a circle.

                                      TABLE 1                                     __________________________________________________________________________                         Examples                                                                      1     2     3     4     5    6                           __________________________________________________________________________    Compounding ratio (parts by weight)                                           Component (a) Polyamide-6                                                                          48    57    50    48    48   48                          Component (b) Polyphenylene ether                                             Inherent viscosity 0.51                                                                            39    30    --    --    39   39                          Inherent viscosity 0.40                                                                            --    --    41    39    --   --                          Inherent viscosity 0.32                                                                            --    --    --    --    --   --                          Component (c) Block copolymer                                                                      SEBS1650                                                                            SEBS1651                                                                            SEBS1651                                                                            SEBS1652                                                                            H*SBS1                                                                             GX1701                                           13    13     9    13    Note) 13                                                                           13                          Component (d) Maleic anhydride                                                                       0.7   0.7   0.7   0.7   0.7                                                                                0.7                       Physical properties                                                           MFR (g/10 min)         21.4                                                                                30.0                                                                                23.0                                                                                27.4                                                                                27.9                                                                               34.0                      Flexural modulus (kg/cm.sup.2)                                                23° C.        17300 19200 20700 16400 19200                                                                              17400                       80° C.        7000  7200  8300  6500  7500 7700                        Izod impact strength   54.5                                                                                71.6                                                                                52.0                                                                                42.4                                                                                 60.0                                                                              62.6                      (kgcm/cm.sup.2) 23° C.                                                 Heat-resisting aging property (%)                                                                  86    88    82    88    78   91                          Melt viscosity ratio   0.3   1.0   1.4   0.1   0.6                                                                                0.1                       Component (c) dispersion particle size (μm)                                                       1.8   0.2   0.3   1.5   0.5                                                                                0.4                       __________________________________________________________________________                              Comparative example                                                           1     2     3     4    5                            __________________________________________________________________________    Compounding ratio (parts by weight)                                           Component (a) Polyamide-6 48    57    48    46   48                           Component (b) Polyphenylene ether                                             Inherent viscosity 0.51   39    30    --    37   39                           Inherent viscosity 0.40   --    --    --    --   --                           Inherent viscosity 0.32   --    --    39    --   --                           Component (c) Block copolymer                                                                           SEBS1652                                                                            SEBS1726                                                                            SEBS1651                                                                            H*SBS2                                                                             SBS KX65                                               13    13    13    Note) 17                                                                           13                           Component (d) Maleic anhydride                                                                            0.7   0.7   0.7   0.7                                                                                0.7                        Physical properties                                                           MFR (g/10 min)              26.7                                                                                30.1                                                                                38.6                                                                                16.1                                                                               29.7                       Flexural modulus (kg/cm.sup.2)                                                23° C.             14000 12300 14800 21200                                                                              16900                        80° C.             4700  3700  5000  10200                                                                              6800                         Izod impact strength                                                          (kgcm/cm.sup.2) 23° C.                                                                             13.0                                                                                6.1   22.2                                                                                30.2                                                                               57.7                       Heat-resisting aging property (%)                                                                       84     --**  --** 90   26                           Melt viscosity ratio         0.06                                                                                0.005                                                                            12      0.2                                                                                1.0                        Component (c) dispersion particle size (μm)                                                          Not dispersed in                                                                           5       0.05                                                                              0.6                                                  polyphenylene ether                                 __________________________________________________________________________     Note)                                                                         H*SBS1 experimental hydrogenated styrenebutadiene-styrene copolymer           styrene content = 40% by weight                                               H*SBS2 experimental hydrogenated styrenebutadiene-styrene copolymer           styrene content = 60% by weight                                               **Not evaluated.                                                         

COMPARATIVE EXAMPLES 6 to 7

Resin compositions were prepared in the same manner as in Example 3except for using no maleic anhydride (Comparative example 6) or usingtrimellitic anhydride in place of maleic anhydride (Comparative example7), and physical properties of the resin composition were evaluated. Theresults are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                         Comparative example                                                           6       7                                                    ______________________________________                                        MFR (g/10 min)     16.8      25.2                                             Flexural modulus (kg/cm.sup.2)                                                23° C.      20500     19800                                            80° C.      8900      8000                                             Izod impact resistance                                                                           4.0       20.6                                             23° C. (kg · cm/cm.sup.2)                                     Dispersed particle size                                                                          0.3        0.3                                             of Component (c) (μm)                                                      ______________________________________                                    

COMPARATIVE EXAMPLE 8

A resin composition was prepared in the same manner as in Example 1except for replacing the polyphenylene ether resin with a resin havingan inherent viscosity of 0.61 d/g (poly-2,6-dimethyl-1,4-phenyleneether, produced experimentally by Mitsubishi Petrochemistry Co., Ltd.),and physical properties of the resin composition were evaluated. Themelt viscosity ratio of this composition was η_(c) /η_(b) =0.06. Whereasthe secondary dispersion particle size of the block copolymer of thisresin composition was 2.3 microns, it can be admitted that a part of theblock copolymer was localized at an interface between the polyamidephase (continuous phase) and the polyphenylene ether phase (primarydispersion phase). Flexural modulus at 80° C. of the resin compositionwas only 5600 kg/cm² and Izod impact strength was 35.3 kg·cm/cm²,whereby it can be understood that control of the dispersion state of theblock copolymer is required.

EXAMPLES 7 to 9

Resin compositions were prepared in the same manner as in Examples 1, 3and 4 except for replacing the kneading method with the successivefeeding method, and physical properties thereof were evaluated. Using aTEX-30 Model twin screw extruder manufactured by Nippon Seikosho K.K.,from a first inlet portion, a mixture mixing and stirring predeterminedformulating amounts of the polyphenylene ether resin, the blockcopolymer and maleic anhydride, and 10% by weight of the predeterminedamount of the polyamide resin with a super mixer was supplied. Then,remaining amounts of the polyamide resin were supplied from the secondinlet portion. Operation conditions of the extruder were rotating numberof 350 rpm, a setting temperature at the region of the first inletportion of 280° C. and a setting temperature at the region of the secondinlet portion of 265° C. Resin compositions corresponding to Examples 1,3 and 4 are called as Examples 7, 8 and 9, respectively and theevaluated results are shown in Table 3.

COMPARATIVE EXAMPLE 9

A resin composition was prepared in the same manner as in Comparativeexample 8 except for replacing the kneading method with the abovesuccessive feeding method used in Examples 7 to 9, and the sameevaluation tests as in Comparative example 8 were carried out. Theresults are also shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                    Examples      Comparative                                                     7     8       9       example 9                                   ______________________________________                                        MFR (g/10 min)                                                                              19.9    20.6    28.0  20.3                                      Flexural modulus                                                              (kg/cm.sup.2)                                                                 23° C. 17300   19600   17500 16500                                     80° C. 7800    7100    6600  5400                                      Izod impact resistance                                                                      66.5    71.1    44.9  42.0                                      23° C. (kg · cm/cm.sup.2)                                     Dispersed particle size                                                                     1.0     0.1     0.1   2.5*                                      of Component (c) (μm)                                                      ______________________________________                                         *partially existed at an interface.                                      

As can be seen from the above results, it can be understood that thesuccessive feeding method is more effective to improve impact strength.

We claim:
 1. A resin composition comprising:(a) 28 to 78% by weight of apolyamide resin, (b) 20 to 70% by weight of a polyphenylene ether resin,(c) 2 to 40% by weight of a block copolymer composed of an alkenylaromatic polymer and a conjugated diene polymer wherein a content of analkenyl aromatic polymer structure unit is 10 to 45% by weight and atleast 50% of a conjugated diene polymer structure unit is hydrogenatedand (d) at least one compound selected from the group consisting of α,β-unsaturated dicarboxylic acid, an acid anhydride and derivativesthereof with an amount of 0.01 to 10 parts by weight based on 100 partsby weight of the sum of Components (a), (b) and (c),Component (b) beingpresent in Component (a) as a primary dispersed phase, Component (c)forming a secondary dispersed phase in Component (b), an averageparticle size of Component (c) being in the range of 0.01 to 3 micronsand a melt viscosity ratio (η_(c) /η_(b)) of Component (c) and Component(b) being in the range of 0.09 to
 5. 2. The resin composition accordingto claim 1, wherein said composition comprises 35 to 75% by weight ofComponent (a), 20 to 60% by weight of Component (b), 5 to 35% by weightComponent (c), and 0.05 to 5 parts by weight of Component (d) based on100 parts by weight of Components (a), (b) and (c).
 3. The resincomposition according to claim 1, wherein said composition comprises 40to 70% by weight of Component (a), 25 to 50% by weight of Component (b),7 to 30% by weight Component (c), and 0.2 to 2 parts by weight ofComponent (d) based on 100 parts by weight of Components (a), (b) and(c).
 4. The resin composition according to claim 1, wherein a meltviscosity ratio (η_(c) /η_(b)) of Component (c) to Component (b) is inthe range of 0.3 to 3.0.
 5. The resin composition according to claim 1,wherein Component (d) is at least one of maleic anhydride and maleicacid.
 6. The resin composition according to claim 1, wherein saidcomposition is obtained by melting and kneading Components (b), (c) and(d), or Components (b), (c), (d) and a part of Component (a) and thenkneading the remaining Component (a).
 7. The resin composition accordingto claim 1, wherein said composition is obtained by melting and kneadingComponents (b), (c), (d), and 5 to 20% by weight of Component (a) basedon total amount to be formulated and then kneading the remainingComponent (a).